With the increasing use of computer networks for transferring data from one location to another remote location, a need has arisen for securing such data from unauthorized interception and reception. To provide such security, various cryptographic algorithms have been developed; and a transmitter then encrypts the data to be sent to the remote receiver by the use of such an algorithm. A decryption device utilizing the same algorithm is used at the receiver to decrypt the information to present it back in plain text, which then may be handled in any conventional manner at the receiver location.
The cryptographic algorithms and the number of bits used in an encryption key vary from low grade encryption, which is relatively easy to "break" or penetrate to high grade encryption, which typically employs larger keys (employing a greater number of bits), which are much more difficult to "break". Currently, valuable commercial property such as motion pictures, cable television signals, software, copyrighted music, and the like, is encoded in digital format. By utilizing digital formats, the clarity of the original always is maintained; and there is no deterioration in quality, even though the digitalized information may be stored for a long period of time. In addition, when delivery of software, motion pictures, cable television or audio music property to a remote location is desired, all that is necessary is to transmit the digital data representative of this property from a transmitting location to a remote location, which may be anywhere in the world. Modern computers readily can receive and store such information; and transmission links capable of handling this data on a worldwide basis exist.
Properties, such as motion pictures, cable television programs, computer software and the like, are extremely valuable. Without high level encryption of such data when it is transmitted from one location to another, the valuable property being transmitted is subjected to the possibility of widespread piracy. Once such piracy occurs, the underlying value of the original property is greatly diminished, in some cases rendering it nearly valueless. As a result, it is extremely important that whenever such information is transferred by means of transmitting it over telephone lines or any other communications link (such as transmission to and from a satellite), the information is encrypted with a high grade encryption key to scramble the sensitive data. This is done so the protected information not only is unreadable by hackers intercepting the transmission, but further is protected so that even a sophisticated effort at cracking or "breaking" the encryption cannot be accomplished, or can only be accomplished with significant effort.
As valuable information is transmitted worldwide, an additional problem is encountered. Currently, United States government policy prohibits the exportation of "high grade" encryption keys out of the United States. A weaker encryption scheme is permitted to be exported from the United States; but this encryption employs a shorter key (currently 40 bits or less). It has been found that such low grade encryption keys (such as a 40 bit key) can be broken with reasonable effort on behalf a person intent on breaking the encryption code. Thus, the low grade, exportable encryption keys which currently exist are not suitable for protecting the extremely valuable property rights which exist in movies, games, video, software and the like.
Within the United States, for example in the cable television industry, typical cable servers send out games, video and software to customers using a larger high grade encryption key (a multi-bit key which typically is more than a 40-bit encryption scheme). The cable operator considers the encrypted information which is being sent as being privy only to the customer who purchases that particular service. The customer who requests information from the cable operator then is provided with a decryption key for decrypting the requested information. The customer then sends information back to the cable operator indicating that the information was received; and the necessary entitlement transaction is completed. This return information is not as important as the valuable information which originally is encrypted by the cable operator, and which is purchased by the customer. The same size key, however, can be used for transmission in both directions.
It is desirable to provide an encryption system which provides a high level of protection for the transmission of valuable data to a designated recipient, which may be used throughout the world to provide a high level or high grade encryption protection without breaching U.S. government regulations concerning the export of encryption systems.